1. Field of the Invention
The invention relates generally to the field of lithography systems and, more particularly, to management of reaction loads in a lithography tool.
2. Background Art
In the fabrication of integrated circuits, lithographic and projection printing techniques are used. Lithography is a process used to create features on the surface of substrates. Such substrates can include those used in the manufacture of flat panel displays, circuit boards, various integrated circuits, and the like. A frequently used substrate for such applications is a semiconductor wafer. During lithography, exposure optics located within a lithography apparatus project an image in a reticle onto the surface of a semiconductor wafer. The wafer is disposed on a wafer stage. The projected image produces changes in the characteristics of a layer of the wafer. For instance, a photoresist layer deposited on the surface of the wafer is etched with a pattern during the process.
Step-and-scan lithography techniques may be used to expose a wafer. Rather than expose the entire wafer at one time, individual fields are scanned onto the wafer, one at a time. This is done by moving the wafer and reticle simultaneously such that an imaging slot is moved across each field during the scan. The wafer stage is stepped between field exposures to allow multiple copies of the reticle pattern to be exposed over the wafer surface.
As a result, components are required to move in step-and-scan lithography systems. Acceleration of system components during their movement can cause a reaction load or reaction movement in components of the system being moved against, and in the support structure. Reaction movements or reaction loads lead to relative motion between critical components, and possible shaking of the support structure, which leads to reduced operational precision for the lithography system. Hence, what is needed is a method, system, and apparatus for reducing reaction loads, support structure shaking, and relative motion among lithography system components.